Please help me out some questions about units in physics *Great moments in telev
ID: 1777594 • Letter: P
Question
Please help me out some questions about units in physics
*Great moments in television: a. The engineer reported to the captain that the shields were failing. The captain asked the science officer how long they would hold up. The science officer reported that they would last another 47.18 seconds. Without knowing much about shields and photon torpedoes, what do you think of the science officer’s answer? Explain your reasoning. b. The “world’s greatest forensic anthropologist” and the “king of the lab” were at a murder scene. The king of the lab found a worm near the corpse. He said these worms move one foot per day and the worm was 38.3 inches from the body. The world’s greatest forensic anthropologist then calculated that this meant the time of death was three days, four hours, and thirty-six minutes ago. Without knowing much about worms and corpses, what do you think of her calculation?
*The speed of sound can be calculated from atmospheric pressure and density. You could look up the formula but let’s pretend you don’t know how. Standard atmospheric pressure is (very nearly) 100,000 pascals. One pascal is one kilogram per “meter second squared” (1 kg/ (m s2 ) ). Notice that the seconds are squared but the meters are not. The density of air is about 1.2 grams per liter. One liter is 1000 cm3 . a. Using only the information above, estimate the speed of sound in air. b. Now look up a measured value for the speed of sound in air. Calculate the relative error of your estimate. Express your result as a percentage.
Explanation / Answer
1. when the science officer said that they could last for another 47.18 seconds, it meant that after 47.18 sewconds the shields would not be able to control damage from the photon torpedos to below the safely permissible limit of damage under shield cover from a photon torpedo. This sould be happening because of rapidly failing power or component faliure causing the shields to fall at a rate thaT led to the prediction of 47.18 seconds form the science officer
2. assuming the specific worm moved 1 ft -> 12 inches per day, time taken for it to move 38.3 inches, t = 38.3/12 =3.1916 days
hence the time taken by worm to travel thius distance = 3 days, 4 hours, 36 minutes
3. given standard atmospheric pressure, P = 10^5 Pa
density of air = 1.2 g / lit = 1.2*10^-3 kg/10^-3 m^3 = 1.2 kg/m^3
now consider unit of P/rho = kg*m^3 /s^2*m*kg = (m/s)^2
hence speed of sound would be about sqroot(P/rho) = 288.675 m/s in air
actual speed of sound in air c = 334 m/s
hence relative error = (344 - 288.675)*100/334 = 13.57 %